Change $drop() input from columns to ...

[etiennebacher]

Close #913

[eitsupi]

I suspect this is a potentially breaking change.
In other words, if you specify it with the columns argument instead of the position argument, won't unexpected behavior occur?

[etiennebacher]

Good catch. Actually I think there's a bug in dots_to_colnames() because passing c() in second values doesn't work:

### this works
pl$DataFrame(mtcars)$drop(c("mpg", "drat"), "hp") |> ncol()
[1] 8

### this doesn't
pl$DataFrame(mtcars)$drop("hp", c("mpg", "drat")) |> ncol()

Error: Execution halted with the following contexts
   0: In R: in $drop():
   0: During function call [ncol(pl$DataFrame(mtcars)$drop("hp", c("mpg", "drat")))]
   1: When constructing a Column Expr
   2: The argument [ `...` ] caused an error
   3: Possibly because element no. [1] 
   4: Expected a value of type [alloc::string::String]
   5: Got value [Rvalue: ["mpg", "drat"], Rsexp: Strings, Rclass: ["character"]]

[eitsupi]

This is a problem of pl$col(), not dots_to_colnames().

> library(polars)

> pl$col(c("mpg", "drat"), "hp")
polars Expr: cols(["mpg", "drat", "hp"])

> pl$col("hp", c("mpg", "drat"))
Error: Execution halted with the following contexts
   0: In R: in pl$col()
   0: During function call [pl$col("hp", c("mpg", "drat"))]
   1: When constructing a Column Expr
   2: The argument [ `...` ] caused an error
   3: Possibly because element no. [1] 
   4: Expected a value of type [alloc::string::String]
   5: Got value [Rvalue: ["mpg", "drat"], Rsexp: Strings, Rclass: ["character"]]

> pl$col("hp", name = c("mpg", "drat"))
polars Expr: cols(["mpg", "drat", "hp"])

> pl$col("hp", columns = c("mpg", "drat"))
Error: Execution halted with the following contexts
   0: In R: in pl$col()
   0: During function call [pl$col("hp", columns = c("mpg", "drat"))]
   1: When constructing a Column Expr
   2: The argument [ `...` ] caused an error
   3: Possibly because element no. [1] 
   4: Expected a value of type [alloc::string::String]
   5: Got value [Rvalue: ["mpg", "drat"], Rsexp: Strings, Rclass: ["character"]]

We should rewrite pl$col()...(#912)

[eitsupi]

Something like pl$DataFrame(mtcars)$drop(columns = c("mpg", "drat")) works in the main branch, but should fail in this PR because of pl$col(name = "", ...).

[etiennebacher]

Indeed, I've updated news, thanks